1. Field of the Invention
The present invention relates generally to cartridge devices adapted for storing and dispensing air-curable viscous fluids, such as caulking compounds, sealing compounds and the like. More particularly, the present invention relates to a substantially airtight cartridge that includes a novel plunger adapted for inserting in the back end of the cartridge body, without taking in or trapping air.
2. Description of the Prior Art
Sealing compounds and the like that cure under the effect of atmospheric moisture (e.g., silicone sealants, polyurethane sealants, polysulfide sealants, etc.) are in wide use in the fields of civil engineering and construction. Examples include the waterproof sealing of window frames, joints, and so forth. While those skilled in the art will recognize that the present invention is useful for storing and dispensing all such viscous fluids, for the sake of simplicity the term "sealant" is use herein to describe such viscous fluids.
Sealant cartridges generally comprise: a tubular cartridge body in which the sealant is disposed; a discharge element such as a nozzle at one end of the cartridge body; and a cylindrical plunger, which is adapted for being received in the other end of the tubular cartridge body and which is axially slidable therein so as to permit the sealant to be extruded from the discharge element. The prior art describes various types of substantially airtight sealant cartridges which isolate the sealant therein from atmospheric moisture and thus secure long-term storage stability. Examples of the prior art include: a sealant cartridge that is characterized by the application of a flame-coated film of ceramic or metal on the circumference of the plunger (Japanese Utility Model Application Laid-Open [Kokai or Unexamined] Number 59-19569 [19,569/1984]); a sealant cartridge that is characterized by the application of a paint sealing film on the rear interior surface of the cartridge body or on the circumference of the plunger (Japanese Patent Application Laid-Open Number 60-68272 [68,272/1985]); and a sealant cartridge that is characterized by the application of a wax-based sealing agent to the rear interior surface of the cartridge body and by the installation of a ringshaped projection along the circumference of the cartridge body in part of the aforesaid sealing agent (Japanese Patent Application Laid-Open Number 63-67276 [67,276/1988]).
As used herein the term "sealing agent" refers not to the sealant disposed in the cartridge and dispensed therefrom but to a compound or mixture which prevents air leakage to the sealant at the interior wall of the cartridge body and the circumferential surface of the plunger.
The prior art sealant cartridges still suffer from the particular deficiency that the sealant at the end of the cartridge associated with the plunger cures during long-term storage. This occurs because air is trapped at that end of the cartridge body when the plunger is inserted therein, after the sealant has been filled into the cartridge body. To counter this, the filling process must be supplemented with a separate process that removes the residual air trapped at the rear of the cartridge body, but such a measure impairs the productivity of the filling operation.
The present invention overcomes the drawbacks of the prior art by providing a sealant cartridge wherein the plunger can be inserted into a sealant-filled cartridge body without taking in or trapping air.